Limestone applied at the rate of 6.7 metric tons/ha to a raw peat soil (pH 3.7) increased the yield of potatoes in a field experiment by 5.5 tons/ha. Higher rates of lime gave no further increase. In the three subsequent years the yield was just as satisfactory on the unlimed plots as on those receiving the 6.7-ton rate and the yield was depressed by higher rates of lime.Limestone, particularly at the higher rates, tended to increase hygroscopic moisture, volume weight, ash, CEC and solubility in pyrophosphate solution and to decrease C and the C/N ratio of the soil. Although these changes were small they were indicative of a beneficial effect of lime on humification of the peat.